scholarly journals Structurally distinct telomere-binding proteins in Ustilago maydis execute non-overlapping functions in telomere replication, recombination, and protection

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Eun Young Yu ◽  
Syed S. Zahid ◽  
Swapna Ganduri ◽  
Jeanette H. Sutherland ◽  
Min Hsu ◽  
...  
Keyword(s):  
Functional Diversity ◽  
Transcriptional Repression ◽  
Binding Proteins ◽  
Ustilago Maydis ◽  
Sequence Specificity ◽  
Telomere Repeat ◽  
Growth Defects ◽  
Domain Structures ◽  
Telomere Protein ◽  
Telomere Replication

AbstractDuplex telomere binding proteins exhibit considerable structural and functional diversity in fungi. Herein we interrogate the activities and functions of two Myb-containing, duplex telomere repeat-binding factors in Ustilago maydis, a basidiomycete that is evolutionarily distant from the standard fungi. These two telomere-binding proteins, UmTay1 and UmTrf2, despite having distinct domain structures, exhibit comparable affinities and sequence specificity for the canonical telomere repeats. UmTay1 specializes in promoting telomere replication and an ALT-like pathway, most likely by modulating the helicase activity of Blm. UmTrf2, in contrast, is critical for telomere protection; transcriptional repression of Umtrf2 leads to severe growth defects and profound telomere aberrations. Comparative analysis of UmTay1 homologs in different phyla reveals broad functional diversity for this protein family and provides a case study for how DNA-binding proteins can acquire and lose functions at various chromosomal locations. Our findings also point to stimulatory effect of telomere protein on ALT in Ustilago maydis that may be conserved in other systems.

scholarly journals Structurally distinct duplex telomere repeat-binding proteins in Ustilago maydis execute specialized, non-overlapping functions in telomere recombination and telomere protection

2020 ◽  
Author(s):  
Eun Young Yu ◽  
Syed Zahid ◽  
Min Hsu ◽  
Jeanette Sutherland ◽  
William K. Holloman ◽  
...  
Keyword(s):  
Functional Diversity ◽  
Transcriptional Repression ◽  
Binding Proteins ◽  
Critical Role ◽  
Ustilago Maydis ◽  
Sequence Specificity ◽  
Telomere Repeat ◽  
Telomere Protection ◽  
Telomere Protein ◽  
Telomere Replication

AbstractDuplex telomere binding proteins exhibit considerable structural and functional diversity in different phyla. Herein we address the distinct properties and functions of two Myb-containing, duplex telomere repeat-binding factors in Ustilago maydis, a basidiomycete fungus that is evolutionarily distant from the standard budding and fission yeasts. The two telomere-binding proteins in U. maydis, named UmTrf1 and UmTrf2, have different domain organizations and belong to distinct protein families with different phylogenetic distributions. Despite these differences, they exhibit comparable affinities and similar sequence specificity for the canonical, 6-base-pair telomere repeats. Deletion of trf1 triggers preferential loss of long telomere tracts, suggesting a role for the encoded protein in promoting telomere replication. Trf1 loss also partially suppresses the ALT-like phenotypes of ku70-deficient mutants, suggesting a novel role for a telomere protein in stimulating ALT-related pathways. In keeping with these ideas, we found that purified Trf1 can modulate the helicase activity of Blm, a conserved telomere replication and recombination factor. In contrast, trf2 appears to be essential and transcriptional repression of this gene leads to severe growth defects and profound telomere aberrations that encompass telomere length heterogeneity, accumulation of extrachromosomal telomere repeats such as C-circles, and high levels of single-stranded telomere DNA. These observations support a critical role for UmTrf2 in telomere protection. Together, our findings point to a unique, unprecedented division of labor between the two major duplex telomere repeat-binding factors in Ustilago maydis. Comparative analysis of UmTrf1 homologs in different phyla reveals a high degree of functional diversity for this protein family, and provides a case study for how a sequence-specific DNA binding protein can acquire and lose functions at different chromosomal locations.

scholarly journals Analysis of Ustilago maydis pot1 reveals context-dependent, dichotomous regulation of homology-directed DNA repair factors by a telomere protein

2021 ◽  
Author(s):  
Syed S. Zahid ◽  
Sarah Aloe ◽  
Jeanette Sutherland ◽  
William K. Holloman ◽  
Neal F. Lue
Keyword(s):  
Dna Repair ◽  
Transcriptional Repression ◽  
Ustilago Maydis ◽  
Telomere Maintenance ◽  
Telomere Repeat ◽  
Homology Directed Repair ◽  
Telomere Protein ◽  
Genetic Mechanisms ◽  
Context Dependent ◽  
Telomere Regulation

AbstractThe telomere G-strand binding protein Pot1 plays multifaceted roles in telomere maintenance and protection. We examined the biochemical activity and genetic mechanisms of Pot1 in Ustilago maydis, a fungal model that recapitulates key features of mammalian telomere regulation. We found that U. maydis Pot1 binds directly to Rad51 and regulates the latter’s strand exchange activity. Deleting an N-terminal domain of Pot1 implicated in Rad51-binding caused telomere shortening, suggesting that Pot1-Rad51 interaction facilitates telomere replication. Depleting Pot1 through transcriptional repression triggered growth arrest as well as rampant recombination, leading to multiple telomere aberrations. In addition, telomere repeat RNAs transcribed from both the G- and C-strand were dramatically up-regulated, and this was accompanied by elevated levels of telomere RNA-DNA hybrids. Telomere abnormalities of pot1-deficient cells were suppressed, and cell viability was rescued by the deletion of rad51 or brh2 (the BRCA2 ortholog), indicating that homology-directed repair (HDR) proteins are key mediators of telomere aberrations and cellular toxicity. Together, these observations underscore the complex physical and functional interactions between Pot1 and DNA repair factors, leading to context-dependent and dichotomous effects of HDR proteins on telomere maintenance and protection.

Structural and Functional Diversity of Hyaluronan-Binding Proteins

2004 ◽  
pp. 189-204 ◽  
Author(s):  
CHARLES D. BLUNDELL ◽  
NICHOLAS T. SEYFRIED ◽  
ANTHONY J. DAY
Keyword(s):  
Functional Diversity ◽  
Binding Proteins ◽  
Hyaluronan Binding

scholarly journals TEN1 Is Essential for CDC13-Mediated Telomere Capping

Genetics ◽  
2009 ◽  
Vol 183 (3) ◽  
pp. 793-810 ◽  
Author(s):  
Ling Xu ◽  
Ruben C. Petreaca ◽  
Hovik J. Gasparyan ◽  
Stephanie Vu ◽  
Constance I. Nugent
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
High Temperatures ◽  
De Novo ◽  
Temperature Sensitive ◽  
Single Stranded Dna ◽  
Growth Defects ◽  
Telomere Capping ◽  
Telomere Replication ◽  
Essential Function

Telomere binding proteins protect chromosome ends from degradation and mask chromosome termini from checkpoint surveillance. In Saccharomyces cerevisiae, Cdc13 binds single-stranded G-rich telomere repeats, maintaining telomere integrity and length. Two additional proteins, Ten1 and Stn1, interact with Cdc13 but their contributions to telomere integrity are not well defined. Ten1 is known to prevent accumulation of aberrant single-stranded telomere DNA; whether this results from defective end protection or defective telomere replication is unclear. Here we report our analysis of a new group of ten1 temperature-sensitive (ts) mutants. At permissive temperatures, ten1-ts strains display greatly elongated telomeres. After shift to nonpermissive conditions, however, ten1-ts mutants accumulate extensive telomeric single-stranded DNA. Cdk1 activity is required to generate these single-stranded regions, and deleting the EXO1 nuclease partially suppresses ten1-ts growth defects. This is similar to cdc13-1 mutants, suggesting ten1-ts strains are defective for end protection. Moreover, like Cdc13, our analysis reveals Ten1 promotes de novo telomere addition. Interestingly, in ten1-ts strains at high temperatures, telomeric single-stranded DNA and Rad52-YFP repair foci are strongly induced despite Cdc13 remaining associated with telomeres, revealing Cdc13 telomere binding is not sufficient for end protection. Finally, unlike cdc13-1 mutants, ten1-ts strains display strong synthetic interactions with mutations in the POLα complex. These results emphasize that Cdc13 relies on Ten1 to execute its essential function, but leave open the possibility that Ten1 has a Cdc13-independent role in DNA replication.

scholarly journals Interaction of Sox2 with RNA binding proteins in mouse embryonic stem cells

2019 ◽  
Author(s):  
Samudyata ◽  
Paulo P. Amaral ◽  
Pär G. Engström ◽  
Samuel C. Robson ◽  
Michael L. Nielsen ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Embryonic Stem ◽  
Messenger Rnas ◽  
Heterochromatin Protein 1 ◽  
Non Coding Rna ◽  
Rna Immunoprecipitation ◽  
Mes Cells

AbstractSox2 is a master transcriptional regulator of embryonic development. In this study, we determined the protein interactome of Sox2 in the chromatin and nucleoplasm of mouse embryonic stem (mES) cells. Apart from canonical interactions with pluripotency-regulating transcription factors, we identified interactions with several chromatin modulators, including members of the heterochromatin protein 1 (HP1) family, suggesting a role of Sox2 in chromatin-mediated transcriptional repression. Sox2 was also found to interact with RNA binding proteins (RBPs), including proteins involved in RNA processing. RNA immunoprecipitation followed by sequencing revealed that Sox2 associates with different messenger RNAs, as well as small nucleolar RNA Snord34 and the non-coding RNA 7SK. 7SK has been shown to regulate transcription at regulatory regions, which could suggest a functional interaction with Sox2 for chromatin recruitment. Nevertheless, we found no evidence of Sox2 modulating recruitment of 7SK to chromatin when examining 7SK chromatin occupancy by Chromatin Isolation by RNA Purification (ChIRP) in Sox2 depleted mES cells. In addition, knockdown of 7SK in mES cells did not lead to any change in Sox2 occupancy at 7SK-regulated genes. Thus, our results show that Sox2 extensively interact with RBPs, and suggest that Sox2 and 7SK co-exist in a ribonucleoprotein complex whose function is not to regulate chromatin recruitment, but might rather regulate other processes in the nucleoplasm.Summary blurbSox2 interacts with RNA-binding proteins and diverse RNAs

scholarly journals Transcriptional repression in Saccharomyces cerevisiae by a SIN3-LexA fusion protein

1993 ◽  
Vol 13 (3) ◽  
pp. 1805-1814
Author(s):  
H Wang ◽  
D J Stillman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Binding ◽  
Fusion Protein ◽  
Protein Interactions ◽  
Transcriptional Repression ◽  
Binding Proteins ◽  
Dna Binding Proteins ◽  
Predicted Amino Acid Sequence

The yeast SIN3 gene (also known as SDI1, UME4, RPD1, and GAM2) has been identified as a transcriptional regulator. Previous work has led to the suggestion that SIN3 regulates transcription via interactions with DNA-binding proteins. Although the SIN3 protein is located in the nucleus, it does not bind directly to DNA in vitro. We have expressed a LexA-SIN3 fusion protein in Saccharomyces cerevisiae and show that this fusion protein represses transcription from heterologous promoters that contain lexA operators. The predicted amino acid sequence of the SIN3 protein contains four copies of a paired amphipathic helix (PAH) motif, similar to motifs found in HLH (helix-loop-helix) and TPR (tetratricopeptide repeat) proteins, and these motifs are proposed to be involved in protein-protein interactions. We have conducted a deletion analysis of the SIN3 gene and show that the PAH motifs are required for SIN3 activity. Additionally, the C-terminal region of the SIN3 protein is sufficient for repression activity in a LexA-SIN3 fusion, and deletion of a PAH motif in this region inactivates this repression activity. A model is presented in which SIN3 recognizes specific DNA-binding proteins in vivo in order to repress transcription.

scholarly journals Differential Contributions of DNA-Binding Proteins to Polycomb Response Element Activity at the Drosophila giant Gene

Genetics ◽  
2020 ◽  
Vol 214 (3) ◽  
pp. 623-634
Author(s):  
Elnaz Ghotbi ◽  
Kristina Lackey ◽  
Vicki Wong ◽  
Katie T. Thompson ◽  
Evan G. Caston ◽  
...  
Keyword(s):  
Dna Binding ◽  
Dna Sequences ◽  
Transcriptional Repression ◽  
Binding Proteins ◽  
Target Genes ◽  
Dna Binding Proteins ◽  
Polycomb Group ◽  
Link Type ◽  
Element Activity

Polycomb-group (PcG) proteins are evolutionarily conserved epigenetic regulators whose primary function is to maintain the transcriptional repression of target genes. Recruitment of Drosophila melanogaster PcG proteins to target genes requires the presence of one or more Polycomb Response Elements (PREs). The functions or necessity for more than one PRE at a gene are not clear and individual PREs at some loci may have distinct regulatory roles. Various combinations of sequence-specific DNA-binding proteins are present at a given PRE, but only Pleiohomeotic (Pho) is present at all strong PREs. The giant (gt) locus has two PREs, a proximal PRE1 and a distal PRE2. During early embryonic development, Pho binds to PRE1 ∼30-min prior to stable binding to PRE2. This observation indicated a possible dependence of PRE2 on PRE1 for PcG recruitment; however, we find here that PRE2 recruits PcG proteins and maintains transcriptional repression independently of Pho binding to PRE1. Pho-like (Phol) is partially redundant with Pho during larval development and binds to the same DNA sequences in vitro. Although binding of Pho to PRE1 is dependent on the presence of consensus Pho-Phol-binding sites, Phol binding is less so and appears to play a minimal role in recruiting other PcG proteins to gt. Another PRE-binding protein, Sp1/Kruppel-like factor, is dependent on the presence of Pho for PRE1 binding. Further, we show that, in addition to silencing gene expression, PcG proteins dampen transcription of an active gene.

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